<template>
  <div
    class="el-tree-node"
    @click.stop="handleClick"
    @contextmenu="($event) => this.handleContextMenu($event)"
    v-show="node.visible"
    :class="{
      'is-expanded': expanded,
      'is-current': node.isCurrent,
      'is-hidden': !node.visible,
      'is-focusable': !node.disabled,
      'is-checked': !node.disabled && node.checked,
    }"
    role="treeitem"
    tabindex="-1"
    :aria-expanded="expanded"
    :aria-disabled="node.disabled"
    :aria-checked="node.checked"
    :draggable="tree.draggable"
    @dragstart.stop="handleDragStart"
    @dragover.stop="handleDragOver"
    @dragend.stop="handleDragEnd"
    @drop.stop="handleDrop"
    ref="node">
    <div class="el-tree-node__content" :style="{ 'padding-left': (node.level - 1) * tree.indent + 'px' }">
      <span
        @click.stop="handleExpandIconClick"
        :class="[
          { 'is-leaf': node.isLeaf, expanded: !node.isLeaf && expanded },
          'el-tree-node__expand-icon',
          tree.iconClass ? tree.iconClass : 'el-icon-caret-right',
        ]">
      </span>
      <el-checkbox
        v-if="showCheckbox"
        v-model="node.checked"
        :indeterminate="node.indeterminate"
        :disabled="!!node.disabled"
        @click.native.stop
        @change="handleCheckChange">
      </el-checkbox>
      <span v-if="node.loading" class="el-tree-node__loading-icon el-icon-loading"> </span>
      <node-content :node="node"></node-content>
    </div>
    <div v-if="childrenLength < infiniteScrollSize">
      <el-collapse-transition>
        <div
          class="el-tree-node__children"
          v-if="!renderAfterExpand || childNodeRendered"
          v-show="expanded"
          role="group"
          :aria-expanded="expanded">
          <infinite-scroll-tree-node
            :render-content="renderContent"
            v-for="child in node.childNodes"
            :render-after-expand="renderAfterExpand"
            :show-checkbox="showCheckbox"
            :key="getNodeKey(child)"
            :node="child"
            @node-expand="handleChildNodeExpand">
          </infinite-scroll-tree-node>
        </div>
      </el-collapse-transition>
    </div>
    <div v-else>
      <el-collapse-transition>
        <div
          class="el-tree-node__children"
          v-if="!renderAfterExpand || childNodeRendered"
          v-show="expanded"
          role="group"
          :aria-expanded="expanded">
          <ul
            class="infinite-list"
            v-infinite-scroll="loadInfiniteScrollTreeNode"
            infinite-scroll-distance="50"
            infinite-scroll-delay="0"
            style="height: 400px; margin-top: 5px; margin-bottom: 5px; overflow: auto">
            <infinite-scroll-tree-node
              :render-content="renderContent"
              v-for="child in infiniteScrollTreeNodes"
              :render-after-expand="renderAfterExpand"
              :show-checkbox="showCheckbox"
              :key="getNodeKey(child)"
              :node="child"
              @node-expand="handleChildNodeExpand">
            </infinite-scroll-tree-node>
          </ul>
        </div>
      </el-collapse-transition>
    </div>
  </div>
</template>

<script type="text/jsx">
import ElCollapseTransition from 'element-ui/src/transitions/collapse-transition';
import ElCheckbox from 'element-ui/packages/checkbox';
import emitter from 'element-ui/src/mixins/emitter';
import {getNodeKey} from './model/util';

export default {
  name: 'InfiniteScrollTreeNode',

  componentName: 'InfiniteScrollTreeNode',

  mixins: [emitter],
  props: {
    node: {
      default() {
        return {};
      }
    },
    props: {},
    renderContent: Function,
    renderAfterExpand: {
      type: Boolean,
      default: true
    },
    showCheckbox: {
      type: Boolean,
      default: false
    }
  },

  components: {
    ElCollapseTransition,
    ElCheckbox,
    NodeContent: {
      props: {
        node: {
          required: true
        }
      },
      render(h) {
        const parent = this.$parent;
        const tree = parent.tree;
        const node = this.node;
        const {data, store} = node;
        return (
          parent.renderContent
            ? parent.renderContent.call(parent._renderProxy, h, {_self: tree.$vnode.context, node, data, store})
            : tree.$scopedSlots.default
              ? tree.$scopedSlots.default({node, data})
              : <span class="el-tree-node__label">{node.label}</span>
        );
      }
    }
  },

  data() {
    return {
      tree: null,
      expanded: false,
      childNodeRendered: false,
      oldChecked: null,
      oldIndeterminate: null,
      childrenLength: 0,
      infiniteScrollTreeNodes: [],
      infiniteScrollSize: 500
    };
  },

  watch: {
    'node.indeterminate'(val) {
      this.handleSelectChange(this.node.checked, val);
    },

    'node.checked'(val) {
      this.handleSelectChange(val, this.node.indeterminate);
    },

    'node.expanded'(val) {
      this.$nextTick(() => this.expanded = val);
      if (val) {
        this.childNodeRendered = true;
      }
    }
  },

  methods: {
    getNodeKey(node) {
      return getNodeKey(this.tree.nodeKey, node.data);
    },

    handleSelectChange(checked, indeterminate) {
      if (this.oldChecked !== checked && this.oldIndeterminate !== indeterminate) {
        this.tree.$emit('check-change', this.node.data, checked, indeterminate);
      }
      this.oldChecked = checked;
      this.indeterminate = indeterminate;
    },

    handleClick() {
      const store = this.tree.store;
      store.setCurrentNode(this.node);
      this.tree.$emit('current-change', store.currentNode ? store.currentNode.data : null, store.currentNode);
      this.tree.currentNode = this;
      if (this.tree.expandOnClickNode) {
        this.handleExpandIconClick();
      }
      if (this.tree.checkOnClickNode && !this.node.disabled) {
        this.handleCheckChange(null, {
          target: {checked: !this.node.checked}
        });
      }
      this.tree.$emit('node-click', this.node.data, this.node, this);
    },

    handleContextMenu(event) {
      if (this.tree._events['node-contextmenu'] && this.tree._events['node-contextmenu'].length > 0) {
        event.stopPropagation();
        event.preventDefault();
      }
      this.tree.$emit('node-contextmenu', event, this.node.data, this.node, this);
    },

    handleExpandIconClick() {
      if (this.node.isLeaf) return;
      if (this.expanded) {
        this.tree.$emit('node-collapse', this.node.data, this.node, this);
        this.node.collapse();
      } else {
        this.node.expand();
        this.$emit('node-expand', this.node.data, this.node, this);
      }
    },

    handleCheckChange(value, ev) {
      this.node.setChecked(ev.target.checked, !this.tree.checkStrictly);
      this.$nextTick(() => {
        const store = this.tree.store;
        this.tree.$emit('check', this.node.data, {
          checkedNodes: store.getCheckedNodes(),
          checkedKeys: store.getCheckedKeys(),
          halfCheckedNodes: store.getHalfCheckedNodes(),
          halfCheckedKeys: store.getHalfCheckedKeys(),
        });
      });
    },

    handleChildNodeExpand(nodeData, node, instance) {
      this.broadcast('ElTreeNode', 'tree-node-expand', node);
      this.tree.$emit('node-expand', nodeData, node, instance);
    },

    handleDragStart(event) {
      if (!this.tree.draggable) return;
      this.tree.$emit('tree-node-drag-start', event, this);
    },

    handleDragOver(event) {
      if (!this.tree.draggable) return;
      this.tree.$emit('tree-node-drag-over', event, this);
      event.preventDefault();
    },

    handleDrop(event) {
      event.preventDefault();
    },

    handleDragEnd(event) {
      if (!this.tree.draggable) return;
      this.tree.$emit('tree-node-drag-end', event, this);
    },

    loadInfiniteScrollTreeNode() {
      let showNodesLength = this.infiniteScrollTreeNodes.length;
      if (this.node.childNodes.length > showNodesLength) {
        this.infiniteScrollTreeNodes[showNodesLength] = this.node.childNodes[showNodesLength];
        this.$set(this.infiniteScrollTreeNodes, showNodesLength, this.node.childNodes[showNodesLength]);
      }
    }
  },

  created() {
    const parent = this.$parent;

    if (parent.isTree) {
      this.tree = parent;
    } else {
      this.tree = parent.tree;
    }

    const tree = this.tree;
    if (!tree) {
      console.warn('Can not find node\'s tree.');
    }

    const props = tree.props || {};
    const childrenKey = props['children'] || 'children';

    this.$watch(`node.data.${childrenKey}`, () => {
      this.node.updateChildren();
    });

    if (this.node.expanded) {
      this.expanded = true;
      this.childNodeRendered = true;
    }

    if (this.tree.accordion) {
      this.$on('tree-node-expand', node => {
        if (this.node !== node) {
          this.node.collapse();
        }
      });
    }

    this.childrenLength = this.node.childNodes.length;
    if (this.childrenLength >= this.infiniteScrollSize) {
      for (let i = 0; i < this.infiniteScrollSize; i++) {
        this.infiniteScrollTreeNodes[i] = this.node.childNodes[i];
      }
    }
  }
};
</script>
